U.S. patent number 9,522,611 [Application Number 14/644,285] was granted by the patent office on 2016-12-20 for inverted pendulum vehicle.
This patent grant is currently assigned to MURATA MANUFACTURING CO., LTD.. The grantee listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Masayuki Kubo, Kenichi Shirato, Shigeru Tsuji.
United States Patent |
9,522,611 |
Tsuji , et al. |
December 20, 2016 |
Inverted pendulum vehicle
Abstract
A tire angular velocity controller (211) is input with a
difference between a target value of a rotational angular velocity
of 0 for main wheels (11) and a rotational angular velocity of the
main wheels (11), which is a differential value of a signal output
from a main wheels rotary encoder (26). The tire angular velocity
controller (211) calculates an inclination angle for the main body
(10) that will cause the difference to become zero. In a second
control mode, the calculated inclination angle is used as a target
inclination angle and the difference between this target
inclination angle and the inclination angle of the main body (10)
at the present time input from an inclination angle sensor (20) is
input to a main body inclination angle controller (212).
Inventors: |
Tsuji; Shigeru (Kyoto,
JP), Shirato; Kenichi (Kyoto, JP), Kubo;
Masayuki (Kyoto, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Kyoto |
N/A |
JP |
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Assignee: |
MURATA MANUFACTURING CO., LTD.
(Kyoto, JP)
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Family
ID: |
50341022 |
Appl.
No.: |
14/644,285 |
Filed: |
March 11, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150183340 A1 |
Jul 2, 2015 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/JP2013/069588 |
Jul 19, 2013 |
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Foreign Application Priority Data
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Sep 18, 2012 [JP] |
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2012-204012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05D
1/0891 (20130101); B60L 7/24 (20130101); B60L
15/10 (20130101); B60L 15/20 (20130101); B60L
3/00 (20130101); B62K 11/007 (20161101); B60L
2240/423 (20130101); B60L 2200/16 (20130101); B60L
2240/463 (20130101); Y02T 10/70 (20130101); Y02T
10/64 (20130101); B60L 2260/34 (20130101); Y02T
10/72 (20130101) |
Current International
Class: |
B60L
15/10 (20060101); G05D 1/08 (20060101); B60L
3/00 (20060101); B60L 7/24 (20060101); B60L
11/18 (20060101); B60L 15/20 (20060101); B62K
3/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2007-336785 |
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Dec 2007 |
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JP |
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2011-168236 |
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Sep 2011 |
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JP |
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Other References
English translation of Written Opinion of the International Search
Authority for Application No. PCT/JP2013/069588 dated Oct. 15,
2013. cited by applicant.
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Primary Examiner: Melton; Todd
Attorney, Agent or Firm: Pearne & Gordon LLP
Claims
The invention claimed is:
1. A moving body comprising: a wheel; a main body for supporting
the wheel rotatably in a pitch direction; a driving control unit
for controlling driving of the wheel; angular change detection
means for detecting an angular change of the main body in the pitch
direction; rotational angle detection means for detecting a
rotational angle of the wheel; and a storage unit for storing a
program implementing a first control mode in which rotation of the
wheel is controlled on the basis of an output of the angular change
detection means such that the angular change of the main body
becomes zero and such that an angle of the main body with respect
to a vertical direction becomes a first angle, and a second control
mode in which rotation of the wheel is controlled on the basis of
an output of the rotational angle detection means such that a
change in the rotational angle of the wheel becomes zero, wherein
the driving control unit implements the first control mode and the
second control mode by reading out and expanding the program, and
the driving control unit includes switching means for switching
between the first control mode and the second control mode, wherein
a part of the main body includes touch detection means for
detecting whether a person is touching the main body, wherein the
switching means switches between the first control mode and the
second control mode in accordance with an output of the touch
detection means, and switches from the second control mode to the
first control mode when a user is touching the grip.
2. The moving body according to claim 1, further comprising
gradient detection means for detecting a ground gradient, wherein
furthermore a torque compensating for a gravitational torque due to
the ground gradient detected by the gradient detection means is
applied in the second control mode.
3. The moving body according to claim 1, further comprising
gradient detection means for detecting a ground gradient, wherein
furthermore an angle of the main body to the vertical direction
compensating for the gravitational torque due to the ground
gradient detected by the gradient detection means is calculated and
the first angle is corrected in the second control mode.
4. The moving body according to claim 1, further comprising
gradient detection means for detecting a ground gradient, wherein
furthermore a torque compensating for a gravitational torque due to
the ground gradient detected by the gradient detection means is
applied in the second control mode.
5. The moving body according to claim 1, further comprising
gradient detection means for detecting a ground gradient, wherein
furthermore an angle of the main body to the vertical direction
compensating for the gravitational torque due to the ground
gradient detected by the gradient detection means is calculated and
the first angle is corrected in the second control mode.
6. The moving body according to claim 1, the switching means
switches from the first control mode to the second control mode
when the user is not touching the grip.
7. The moving body according to claim 1, the switching means
switches from the second control mode to the first control mode
when the user is touching the grip and with a condition where an
inclination angle of the main body is within a certain range.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a moving body that is equipped
with wheels and in particular relates to a moving body that
controls driving of its wheels.
Description of the Related Art
In the related art, a moving body is known that controls driving of
its wheels by performing inverted pendulum control. For example,
Patent Document 1 describes a moving body that is a coaxial
two-wheel vehicle that performs inverted pendulum control and is
equipped with a stabilizing wheel in front of its main wheels.
Patent Document 1: Japanese Unexamined Patent Application
Publication No. 2011-168236
BRIEF SUMMARY OF THE INVENTION
However, in inverted pendulum control, although control is
performed to maintain the inclination angle of a main body at a
certain angle with respect to a vertical direction, control is not
performed to cause the main body to stop in place. Therefore, there
is a possibility that the main body may unintentionally move on a
slope for example due to the gravitational torque generated by the
inclination of the slope.
Accordingly, an object of the present invention is to provide a
moving body that prevents a main body from unintentionally moving
due to the gravitational torque on a slope.
A moving body of the present invention includes a wheel; a main
body for supporting the wheel rotatably in a pitch direction; a
driving control unit for controlling driving of the wheel; angular
change detection means for detecting an angular change of the main
body in the pitch direction; and rotational angle detection means
for detecting a rotational angle of the wheel.
The driving control unit executes a first control mode in which
rotation of the wheel is controlled on the basis of an output of
the angular change detection means such that the angular change of
the main body becomes zero and such that an angle of the main body
with respect to a vertical direction becomes a first angle, and a
second control mode in which rotation of the wheel is controlled on
the basis of an output of the rotational angle detection means such
that a change in the rotational angle of the wheel becomes zero.
The first control mode and the second control mode are switched
between by using switching means.
In the first control mode, the inclination angle of the main body
is maintained at the first angle through inverted pendulum control.
For example, the driving control unit calculates a torque to apply
to the wheel and drives the wheel such that the inclination angle
of the main body with respect to the vertical direction is
maintained at zero and such that the angular velocity is maintained
at zero. In this first control mode, the moving body is in a
freestanding state and control is not performed to stop the main
body in place and therefore a user is able to use the moving body
as a handcart by pushing the main body.
In the first control mode, when a switching instruction is issued
by a selector switch for example, switching to the second control
mode is performed. In the second control mode, control is performed
such that the change in the rotational angle of the wheel becomes
zero. That is, the driving control unit makes a rotational angular
velocity of zero be a target value upon switching to the second
control mode from the first control mode and calculates a torque to
apply to the wheel such that the difference between this target
value and the rotational angular velocity will become zero. For
example, the driving control unit calculates the difference between
a rotational angular velocity of the wheel of 0 and the rotational
angular velocity of the wheel detected at the present time and
calculates an inclination angle of the main body that will make the
difference become zero. The driving control unit calculates a
torque to apply to the wheel such that the inclination angle of the
main body with respect to the vertical direction will become the
calculated inclination angle and such that the angular velocity
will become zero. In the above-described example, the driving
control unit performs control such that the inclination angle of
the main body becomes equal to a target inclination angle, but may
instead simply perform control such that the rotational angular
velocity of the wheel becomes zero.
In the second control mode, the rotational angular velocity of the
wheel remains at zero and therefore the main body remains in place
even if gravitational torque is exerted on a slope. Therefore, it
is possible to prevent the main body from unintentionally moving
due to gravitational torque on a slope.
Switching between the first control mode and the second control
mode may be instructed by the user using their hand, but for
example it also is possible to provide a touch sensor that detects
a person's touch in part of the main body such that the first
control mode is executed when there is a touch and the second
control mode is executed when there is no touch. In this case, it
is possible for the user to go up or down a slope while using the
moving body as a handcart and since the moving body stops in place
when the user releases their hands, safety is improved.
In addition, it is preferable that the moving body of the present
invention include gradient detection means for detecting a ground
gradient (inclination angle of ground with respect to horizontal
plane). In this case, in the second control mode, it is possible to
perform feed forward control in which a torque compensate
compensating for gravitational torque due to a ground gradient is
applied and it is possible to calculate an inclination angle of the
main body to the vertical direction compensating for the
gravitational torque due to the ground gradient and correct the
target inclination angle using feed forward control.
According to the present invention, it is possible to prevent the
main body from unintentionally moving due to the gravitational
torque on a slope.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is an outline view of a coaxial two-wheel vehicle.
FIG. 2 is a control configuration diagram illustrating a
configuration of the coaxial two-wheel vehicle.
FIG. 3 is a block diagram of a control unit 21 at the time of a
first control mode.
FIG. 4 is a block diagram of the control unit 21 at the time of a
second control mode.
FIG. 5 illustrates the relationship between a ground inclination
angle, a main body inclination angle and an intersection angle.
FIG. 6 is a block diagram of the control unit 21 according to
modification 1.
FIG. 7 illustrates the relationship between a ground inclination
angle and a main body inclination angle.
FIG. 8 is a block diagram of the control unit 21 according to
modification 2.
FIG. 9 is a block diagram of the control unit 21 at the time of a
second control mode.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is an outline view of a coaxial two-wheel vehicle 1, which
is an embodiment of a moving body of the present invention. FIG. 2
is a control configuration diagram illustrating a configuration of
the coaxial two-wheel vehicle 1.
The coaxial two-wheel vehicle 1, for example, includes a
rectangular-parallelepiped-shaped main body 10. The main body 10
has a shape that is long in a vertical direction (Z, -Z direction
in figure) and short in a depth direction (Y, Y- direction in
figure). The main body 10 has a control substrate, a battery and so
forth built into the inside thereof.
Main wheels 11 are attached to a right-side (X direction in figure)
end portion and a left-side (-X direction in figure) end portion of
a lower portion of the main body 10 in the vertical direction (-Z
direction). These pair of main wheels 11 are attached to the same
axle and rotate synchronously. However, the main wheels 11 can be
instead driven and made to rotate individually. In addition, in
this embodiment, an example is described in which there are two
main wheels 11, but there may instead be one main wheel 11 or three
or more main wheels 11.
For example, one end of a cylindrical handle 15 is attached to an
upper portion of the main body 10 in the vertical direction and a
T-shaped grip 16 is attached to the other end of the handle 15. A
user interface such as a power supply switch (user I/F 28
illustrated in FIG. 2) is provided on the grip 16. A hand brake 29
is attached to the handle 15 at a position close to the grip 16
(the hand brake is not an essential element in the present
invention). A user is able to grasp the grip 16 or place their
forearms on the grip 16 in order to push the coaxial two-wheel
vehicle 1 through friction between the grip and the user's forearms
or the like.
In reality, a cover is attached to the main body 10 and the
substrate and so forth inside the main body 10 cannot be seen from
the outside.
One end of a rod-shaped support 12 is attached to a back surface of
the main body 10 (-Y direction). This one end of the support 12 is
rotatably connected to the main body 10. A stabilizing wheel 13 is
attached to the other end of the support 12. The support 12
supports the main body 10 and is for preventing the main body 10
from falling over. The support 12 and the stabilizing wheel 13 are
not essential elements in the present invention, but by providing
the stabilizing wheel 13, the coaxial two-wheel vehicle can be
pushed even in a state where the main body 10 is greatly inclined
from the vertical direction when the power is off due to the main
wheels 11 and the stabilizing wheel 13 being in contact with the
ground. In addition, there may be two or more supports 12 and
stabilizing wheels 13.
Next, the configuration and basic operation of the coaxial
two-wheel vehicle 1 will be described. As illustrated in FIG. 2,
the coaxial two-wheel vehicle 1 includes an inclination angle
sensor 20, a control unit 21, a ROM 22, a RAM 23, a gyro sensor 24,
a main wheels driving unit 25, a main wheels rotary encoder 26, a
support rotary encoder 27, the user I/F 28 and the hand brake
29.
The control unit 21 is a functional unit that controls the coaxial
two-wheel vehicle 1 in an integrated manner and implements various
operations by reading out a program stored in the ROM 22 and
expanding the program in the RAM 23. The inclination angle sensor
20 detects an inclination angle of the main body 10 in a pitch
direction (the rotational direction around the axle of main wheels
11 in FIG. 1) with respect to the vertical direction and outputs
the detected inclination angle to the control unit 21. The gyro
sensor 24 detects an angular velocity of the main body 10 in the
pitch direction and outputs the detected angular velocity to the
control unit 21. In addition, the coaxial two-wheel vehicle 1 may
for example further include an acceleration sensor that detects an
acceleration of the main body 10 in each direction and a rotary
encoder that detects a rotational angle of the stabilizing wheel
13.
The main wheels rotary encoder 26 detects a rotational angle of the
main wheels 11 and outputs the detection result to the control unit
21. The support rotary encoder 27 detects an intersection angle,
which is an angle formed by the main body 10 and the support 12,
and outputs the detection result to the control unit 21.
As a basic operation (hereafter, referred to as first control
mode), the control unit 21 detects a change in the inclination
angle of the main body 10 in the pitch direction on the basis of
the detection results of the gyro sensor 24 and the inclination
angle sensor 20 and controls the main wheels driving unit 25 such
that the angular change of the main body 10 in the pitch direction
becomes zero and that the inclination angle of the main body 10
with respect to the vertical direction becomes a first value (zero
or a value close to zero).
FIG. 3 is a block diagram of the control unit 21 at the time of the
first control mode. In the first control mode, the control unit 21
includes a main body inclination angle controller 212 and a main
body inclination angular velocity controller 213. The main body
inclination angle controller 212 is input with the difference
between a target inclination angle (first value: 0.degree. for
example) and the inclination angle of the main body 10 at the
present time input from the inclination angle sensor 20 and
calculates an inclination angular velocity for the main body 10
that will make the difference become 0. The main body inclination
angular velocity controller 213 is input with the difference
between the inclination angular velocity calculated by the main
body inclination angle controller 212 and the inclination angular
velocity of the main body 10 at the current time input from the
gyro sensor 24 and calculates a torque to apply so that the
difference will become zero.
The main wheels driving unit 25 is a functional unit that drives a
motor that causes the axle to which the main wheels 11 are attached
to rotate, and applies the torque calculated by the main body
inclination angular velocity controller 213 to the motor of the
main wheels 11 and thereby causes the main wheels 11 to rotate.
In this way, as the first control mode, the coaxial two-wheel
vehicle 1 performs control such that inverted pendulum control is
performed and the posture of the main body 10 is maintained fixed.
Since the coaxial two-wheel vehicle 1 maintains a fixed posture
even when a user pushes the coaxial two-wheel vehicle 1 by grasping
the grip 16, the coaxial two-wheel vehicle 1 can be used as a
handcart.
Here, an example is illustrated in which the gyro sensor 24 and the
inclination angle sensor 20 are used as means for detecting a
change in the inclination angle of the main body 10 in the pitch
direction, but instead an acceleration sensor can be used or
another type of sensor may be used.
In addition, an example is illustrated in which the main body
inclination angle controller 212 is input with the difference
between a target inclination angle (0.degree. for example) and the
inclination angle of the main body 10 at the present time input
from the inclination angle sensor 20, but instead the target
inclination angle (for example 0.degree.) may be a combination of
the inclination angle of the main body 10 with respect to a
direction orthogonal to the ground and the gradient of the slope.
The inclination angle of the main body 10 with respect to a
direction orthogonal to the ground can be calculated from an
intersection angle between the main body 10 and the support 12
input from the support rotary encoder 27.
For example, as illustrated in FIG. 5, if the intersection angle of
the main body 10 and the support 12 is denoted by .theta..sub.1,
the inclination angle of the main body 10 with respect to a
direction orthogonal to the ground is denoted by .theta..sub.2, the
length of the main body 10 (length from position at which the main
body 10 and the support 12 intersect up to the main wheels 11) is
denoted by L.sub.1 and the length of the support 12 (length from
position at which the main body 10 and the support 12 intersect up
to the stabilizing wheel 13) is denoted by L.sub.2, from the
relation L.sub.1 cos .theta..sub.2=L.sub.2
cos(.theta..sub.1-.theta..sub.2), the inclination angle
.theta..sub.2 of the main body 10 with respect to the direction
orthogonal to the ground can be calculated from the following
expression.
.theta..function..times..times..times..theta..times..times..times..theta.-
.times..times. ##EQU00001##
In this way, as the first control mode, the coaxial two-wheel
vehicle 1 performs control such that inverted pendulum control is
performed and the posture of the main body 10 is maintained fixed.
The coaxial two-wheel vehicle 1 of this embodiment is also able to
execute a second control mode in which the coaxial two-wheel
vehicle 1 continuously remains in place while performing inverted
pendulum control.
FIG. 4 is a block diagram of the control unit 21 at the time of the
second control mode. The control unit 21 at the time of the second
control mode includes a tire angular velocity controller 211 in
addition to the configuration of the control unit 21 at the time of
the first control mode illustrated in FIG. 3. The configurations
and functions of the main body inclination angle controller 212 and
the main body inclination angular velocity controller 213 are the
same as those in the first control mode.
When a switching instruction is issued by a selector switch
provided in the user I/F 28 for example, the first control mode and
the second control mode are switched between. Taking the target
value of the rotational angular velocity .theta..sub.2ref' of the
main wheels 11 to be 0, the tire angular velocity controller 211 is
input with the difference between this target value and the
rotational angular velocity .theta..sub.2' of the main wheels 11 at
the present time, which is a differential value of a signal output
from the main wheels rotary encoder 26. The tire angular velocity
controller 211 calculates an inclination angle .theta..sub.1ref for
the main body 10 that will cause the difference to become zero.
The inclination angle .theta..sub.1ref is given by
.theta..sub.1ref=(1/mgy.sub.g).tau..sub.1 from the relation
.tau..sub.1=mg.theta..sub.1refy.sub.g (here, m is the mass of the
main body 10 and g is the acceleration due to gravity), where
y.sub.g is the center of gravity of the main body 10 and
.tau..sub.1 is the gravitational torque. Then, denoting the main
wheels motor torque as .tau..sub.2, .tau..sub.2=J.theta..sub.2ref''
and .theta..sub.2ref''=(.theta..sub.2ref'-.theta..sub.2')/T (here,
T=time) from the relation between the angular acceleration and the
moment of inertia and therefore if we consider that the
gravitational torque is compensated for by the main wheels motor
torque, since .tau..sub.1=.tau..sub.2,
.theta..times..times.''.times..times..theta..times..times.'.theta.'.times-
..times. ##EQU00002##
Here, the tire angular velocity controller 211 performs integration
processing so that the main body angle inclination angle will be
output as zero when the input difference is instantaneously zero
and the main body 10 will be prevented from moving.
In the second control mode, the calculated inclination angle
becomes the target inclination angle. Then, the difference between
the target inclination angle and the inclination angle of the main
body 10 at the present time input from the inclination angle sensor
20 is input to the main body inclination angle controller 212.
Thus, even if gravitational torque is exerted on a slope and the
main wheels 11 rotate, a torque is calculated that will make the
change in rotational angle become zero and therefore the coaxial
two-wheel vehicle 1 remains in position at the point in time when
switching to the second control mode is performed. Therefore, in
the second control mode, it is possible to prevent the main body 10
from unintentionally moving due to the gravitational torque on a
slope.
In the above-described example, switching between the first control
mode and the second control mode is performed when a switching
instruction is issued by the selector switch, but instead the grip
16 may be provided with a touch sensor and switching from the first
control mode to the second control mode may be performed when it is
detected that the user is not touching the grip 16. In this case,
when it is detected that the user is touching the grip 16,
switching from the second control mode to the first control mode is
performed. In addition, switching from the first control mode to
the second control mode may be performed once a certain period of
time has elapsed after it has been detected that the user's hand
has moved away.
The second control mode does not have to be executed while inverted
pendulum control of the first control mode is being performed, and
an angle control loop may be simply executed in which the vehicle
continues to remain in place without an inverted pendulum control
posture control loop being performed.
That is, as illustrated in FIG. 9, the control unit 21 includes
only a tire angle controller 221 at the time of the second control
mode. A rotational angle .theta..sub.2ref, which is the value of a
signal output from the main wheels rotary encoder 26 at the time
point when switching was performed to the second control mode, is
used as a target value and the tire angle controller 221 is input
with the difference between the target value and a rotational angle
.theta..sub.2 of the main wheels 11 at the present time, which is
the value of a signal output from the main wheels rotary encoder
26. The tire angle controller 221 calculates a torque to apply so
that the difference will become zero. In this case as well, even if
gravitational torque is exerted on a slope and the main wheels 11
rotate, a torque is calculated that will cause the change in
rotational angle to become zero and therefore the coaxial two-wheel
vehicle 1 remains in position at the point in time when switching
to the second control mode is performed.
In the above-described example, a case has been given in which the
detection of touching of the grip 16 by the user is used as a
timing at which switching from the second control mode to the first
control mode is to be performed, but instead a condition where the
inclination angle of the main body 10 is within a certain range
(for example, -5.degree. to -3.degree.) may be adopted as a
switching condition. In the case where this certain range is set so
as to be close to a target value of the inclination angle of the
main body 10 in inverted pendulum control, since the inclination
angle of the main body 10 negligibly changes once inverted pendulum
control has started, the user will not notice anything
untoward.
Next, FIG. 6 is a block diagram of the control unit 21 according to
modification 1. In the second control mode according to
modification 1, in addition to the configuration of the control
unit 21 at the time of the second control mode illustrated in FIG.
4, the control unit 21 is further equipped with a gradient
estimating unit 214 and a torque command generating unit 215. The
configurations and functions of the tire angular velocity
controller 211, the main body inclination angle controller 212 and
the main body inclination angular velocity controller 213 are the
same as those illustrated in FIG. 4.
The gradient estimating unit 214 is input with a value of the
support rotary encoder 27 (that is, the intersection angle
.theta..sub.1 of the main body 10 and the support 12) and the value
of the inclination angle sensor 20 (that is, the inclination angle
.theta..sub.3 of the main body 10 with respect to the vertical
direction) and estimates a ground inclination angle
.theta..sub.h.
As indicated by Math 1, the inclination angle .theta..sub.2 of the
main body 10 with respect to a direction orthogonal to the ground
is obtained from the intersection angle .theta..sub.1, the length
L.sub.1 of the main body and the length L.sub.2 of the support 12.
Thus, the ground inclination angle .theta..sub.h is obtained from
.theta..sub.h=.theta..sub.2+.theta..sub.3.
The torque command generating unit 215 is input with the ground
inclination angle .theta..sub.h estimated by the gradient
estimating unit 214 and calculates a torque value to compensate for
the gravitational torque generated by the ground inclination angle
.theta..sub.h. Therefore, the control unit 21 according to
modification 1 adds the torque value calculated by the torque
command generating unit 215 to the torque value calculated by the
main body inclination angular velocity controller 213 and performs
feed forward control. The gravitational torque .tau..sub.1
generated by the slope, as illustrated in FIG. 7, is given by
.tau..sub.1=FR=mgsin .theta..sub.hR (here, m is the mass of the
main body 10 and g is the acceleration due to gravity), where F is
the propulsive force of the main wheels 11 generated along the
inclination of the slope and R is the tire radius of the main
wheels 11. Therefore, the torque command generating unit 215 adds a
value ".alpha.mgsin .theta..sub.hR" as a correction torque value
obtained by multiplying .tau..sub.1 by a certain feed forward
coefficient .alpha. (.alpha. is 0 to 1) to the torque value
calculated by the main body inclination angular velocity controller
213. Thus, when the main body 10 is on a slope, torque that
compensates for the gravitational torque due to the ground
inclination angle is applied to the main wheels 11 at the time
point when switching to the second control mode is performed and
therefore torque can be applied to the main wheels 11 before
feedback control by the tire angular velocity controller 211
acts.
Next, FIG. 8 is a block diagram of a control unit 21 according to
modification 2. In the second control mode according to
modification 2, in addition to the configuration of the control
unit 21 at the time of the second control mode illustrated in FIG.
4, the control unit 21 is further equipped with the gradient
estimating unit 214 and an inclination angle command generating
unit 216. The configurations and functions of the tire angular
velocity controller 211, the main body inclination angle controller
212 and the main body inclination angular velocity controller 213
are the same as those illustrated in FIG. 4.
The inclination angle command generating unit 216 is input with a
ground inclination angle .theta..sub.h from the gradient estimating
unit 214 and calculates an inclination angle of the main body 10 to
compensate for the gravitational torque generated by the ground
inclination angle .theta..sub.h.
The gravitational torque .tau..sub.1 due to the slope is given by
.tau..sub.1=FR=mgsin .theta..sub.hR, as illustrated in FIG. 7. A
torque counterforce .tau..sub.2 generated due to the inclination
angle of the main body 10 with respect to a vertical direction, is
expressed by .tau..sub.2=mgsin .theta.y.sub.g (here, y.sub.g is the
height of the center of gravity of the main body 10). Therefore,
the inclination angle command generating unit 216 calculates a
corrected inclination angle .theta. such that
.tau..sub.1=.tau..sub.2. Here, if sin .theta. is close to .theta.,
mg.theta..sub.hR=mg.theta.y.sub.g and
.theta.=(R/y.sub.g).theta..sub.h. Therefore, for example, if R=100
mm and y.sub.g=300 mm, the main body 10 is caused to be inclined at
around 1/3 of the ground inclination angle.
The inclination angle command generating unit 216 adds a value
".beta..theta.", which is obtained by multiplying the corrected
inclination angle .theta. calculated as described above by a
certain feed forward coefficient .beta. (.beta. is 0 to 1), to the
inclination angle calculated by the tire angular velocity
controller 211. Thus, since the inclination angle of the main body
10, which is the target, is corrected to an inclination angle of
the main body 10 obtained by compensating for the gravitational
torque due to the ground inclination angle when the main body 10 is
on a slope at the time point when switching to the second control
mode is performed, torque can be applied to the main wheels 11
before feedback control by the tire angular velocity controller 211
acts. 10 . . . main body 11 . . . main wheels 12 . . . support 13 .
. . stabilizing wheel 15 . . . handle 16 . . . grip 20 . . .
inclination angle sensor 21 . . . control unit 22 . . . ROM 23 . .
. RAM 24 . . . gyro sensor 25 . . . main wheels driving unit 26 . .
. main wheels rotary encoder 27 . . . support rotary encoder 29 . .
. hand brake 211 . . . tire angular velocity controller 212 . . .
main body inclination angle controller 213 . . . main body
inclination angular velocity controller
* * * * *